This invention concerns a tooling for sharpening the blades of sharp or cutting tools, and in particular knife blades.
The blades of sharp tools call for regular maintenance in order to preserve their cutting power.
Such maintenance consists of regular sharpening operations during which the cutting edge is corrected using a grindstone or a suitable machine; between two sharpening operations, the wear of the cutting edge is delayed by sharpening operations using a so-called tool sharpening steel, a diabolo-type whetstone or still a sharpening module fitted with (fixed or hinged) cross spindles.
The type of tool sharpening steel used depends on the degree of wear of the blade. Quite often, the operator uses a  less than  less than rough greater than  greater than  sharpening steel to start off, before using a  less than  less than smooth greater than  greater than  finishing sharpening steel acting as a burnisher for the edge of the blade.
But the implementation of these tool sharpening steels calls for high level of technical know-how and an experienced hand; consequently, they cannot be used efficiently by anybody.
Diabolo-type sharpening steels and those with fixed spindles are relatively inefficient and are not able to obtain interesting sharpening quality.
The sharpening modules fitted with cross spindles are used generally to burnish the tool blades and it is interesting to see that they can be used in a satisfactory manner even by people without a long experience or high level of technical know-how as far as sharpening is concerned.
Such a device, described in the document U.S. Pat. No. 5,478,272, consists of a plane base wherein is provided a vertical slot intended for the passage of the blade to be sharpened, and fitted with two sharpening spindles crossing one another opposite said slot. Both sharpening spindles, made of steel wire, are generally curved in shape and they are hinged at their upper end on the plane base, by means of rotary buttons associated with recall springs. These spindles form together a sharpening V which is mobile under the pressure of the tool blade to be sharpened; the corresponding mobile V enables to ensure regular or relatively regular processing pressure on the tool blade.
Lower and upper stops limit the pivoting of said spindles between a high position and a low position.
The structure of this type of device is however relatively complex, in particular due to the presence of recall springs integral with the rotary buttons. Moreover, these springs wear out quite rapidly and it is necessary to replace them on a regular basis, which is not always very easy to realize, and which involves important part and labor costs.
This invention concerns a sharpening device such as the one which has just been described, i.e. with hinged cross spindles, but with simplified structure, hence easier maintenance and cheaper cost price.
Another purpose of this invention is to enhance the guiding of the tool blade to perfect the sharpening quality.
Another purpose still of the invention is to provide in addition to both hinged sharpening spindles acting as a burnisher, a complementary device capable of ensuring enhanced grinding operations of the edge of the tool blade (enhanced operations that are similar to those fulfilled by conventional  less than  less than rough greater than  greater than  sharpening steels).
The device according to this invention, for sharpening the blades of sharp tools, is therefore of the type comprising a plate fitted with an opening letting through the tool blade, opposite which opening are provided two sharpening structures in the form of oblong spindles crossing each other, which sharpening spindles are hinged at one of their ends on said plate, each of one side of said opening, and comprise elastic recall means, in order to obtain a mobile sharpening V under the pressure of the blade to be sharpened.
According to this invention, each sharpening spindle consists of a U-shaped rod comprising two parallel or substantially parallel arms connected at the bottom of the U and both free ends of the U comprise square junctions, forming hinging axes which are accommodated and free to rotate in offset engagement orifices, provided on said plate or on an appropriate support interlocked with said plate, in order to obtain an elastic recall of said sharpening spindles by a twisting effect.
Still according to the invention, both sharpening spindles are generally curved in shape delineating an angle in the order of 40xc2x0 with respect to one another.
Still according to the invention, the plate of the device is fitted with a vertical opening, both sharpening spindles being hinged in the upper section of the supporting plate, on axes perpendicular to the plane of the latter.
According to a preferred embodiment, both sharpening spindles comprise each square junctions oriented in revere direction. In home position, these junctions are advantageously offset from their axes.
The square junctions of the sharpening spindles, which form the hinging axes, may also be extracted easily from their reception, in order to render said spindles removable with a view notably to facilitate their replacement or their cleaning.
According to another interesting particularity, both sharpening spindles are engaged into one another.
According still to another particularity, the sharpening device according to this invention comprises a guiding structure of the tool blade, in the form of two independent plate blades arranged opposite to one another, fixed at their upper end on the plate or on a support interlocked with said plate. Both these blades are spaced from one another in the upper section and they contact one another at their lower end to delineate a self-clamping guiding V, provided just behind both sharpening spindles.
Both these guiding blades are preferably arranged as a dihedron to form a first V flared in the upper section of the opening of the plate, and a second V narrow in its lower section.
Still according to another characteristic, the guiding blades are fitted, in their lower section, with means to grind the edge of the tool blades. These means are advantageously under the form of two single piece tabs each withdrawn from one of the guiding blades and folded in reverse direction with respect to one another to form a grinding V.
According to another particularity, the plate of the sharpening device comprises a single piece tab enabling removable engagement into an appropriate support.